The invention relates to an alternating or direct current sensor for an electronic trip device of an electrical circuit breaker, comprising a tubular-shaped shunt through which said current flows axially and electrical measurement means to measure the potential difference produced at the terminals of said shunt by the current flow.
Electronic trip devices generally comprise current transformers delivering a signal proportional to the current flowing in the circuit breaker. Trip devices of this kind only operate in alternating current and with the development of direct current mains systems and appliances, the need has arisen for a universal current sensor, responding to alternating and direct currents and able to be fitted in circuit breakers, replacing the usual current transformers. It has already been proposed to use Hall effect sensors, but the latter are costly and unsuitable for an electrical circuit breaker environment.
It is known that a shunt resistance enables the current intensity to be calculated from the measurement of the potential difference at the terminals of the resistance through which this current flows. The resistance dissipates energy and this measurement principle is not applicable as such on power circuits, without taking special precautions.
The object of the present invention is to achieve a simple and accurate current sensor which can replace electronic trip device current transformers for measurement of alternating and direct currents.